Abstract
Photosystem II, a large membrane protein complex, catalyzes the important reaction of water oxidation to molecular oxygen. Many PSII subunits are conserved between plants, green algae, and cyanobacteria. The extrinsic proteins that comprise the oxygen evolving complex differ between cyanobacteria and chloroplasts. In the current accepted model, higher plants and green algae have PsbO, PsbP and PsbQ, while cyanobacteria contain PsbO, PsbV and PsbU. Interestingly, homologs of both PsbP and PsbQ have been found according to previous genomic and proteomic analysis in cyanobacterium, Synechocystis 6803. To clarify the function of these two proteins in cyanobacterial PSII, we have analyzed isolated PSII complexes from knockout mutants of both proteins. In this presentation, we demonstrate that the functional roles of PsbP and PsbQ proteins are conserved between cyanobacteria and plants and that five lumenal extrinsic proteins are present in cyanobacterial PSII. [Supported by National Science Foundation]
